WASHINGTON, DC - APRIL 29: Former U.S. President Bill Clinton (R) acknowledges audiences as Holocaust survivor and author Elie Wiesel (2nd R) looks on during the 20th anniversary National Tribute at the United States Holocaust Memorial Museum April 29, 2013 in Washington, DC. The Museum was hosting a two-day tribute event to honor Holocaust survivors and World War II veterans to mark its 20th anniversary. (Photo by Alex Wong/Getty Images)

World War II veterans stand as they are recognized for their service at the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

Photo: Charles Dharapak, Associated Press

World War II veterans stand as they are recognized for their...

World War II veterans stand as they are recognized for their... Photo-4547822.61349 - SFGate

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Military honor guard are illuminated by stage lights as they return to retrieve flags on stage at the end of the ceremony for the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

Photo: Charles Dharapak, Associated Press

Military honor guard are illuminated by stage lights as they return...

Military honor guard are illuminated by stage lights as they return... Photo-4549056.61349 - SFGate

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Audience members comprising of Holocaust survivors, veterans, and family members stand during a moment of silence in a tent sent up across from the museum for the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

Former President Bill Clinton greets audience members after he spoke at the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)

Photo: Charles Dharapak, Associated Press

Former President Bill Clinton greets audience members after he...

Former President Bill Clinton greets audience members after he... Photo-4549053.61349 - SFGate

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Attendees listen to former US president Bill Clinton speak during a ceremony to celebrate the Holocaust Memorial Museum's 20th anniversary in Washington on April 29, 2013. AFP PHOTO/Jewel SamadJEWEL SAMAD/AFP/Getty Images

Photo: Jewel Samad, AFP/Getty Images

Attendees listen to former US president Bill Clinton speak during a...

Attendees listen to former US president Bill Clinton speak during a... Photo-4549048.61349 - SFGate

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WASHINGTON, DC - APRIL 29: Holocaust survivor Romana Strochlitz Primus (C) of New London, Connecticut, whose father Sigmund Strochlitz was the chairman of the museum's Contents Committee, becomes emotional during the 20th anniversary National Tribute at the United States Holocaust Memorial Museum April 29, 2013 in Washington, DC. The Museum was hosting a two-day tribute event to honor Holocaust survivors and World War II veterans to mark its 20th anniversary. (Photo by Alex Wong/Getty Images)

World War II veteran Scottie Ooton (center) who helped to liberate a concentration camp and Holocaust survivor and author Elie Wiesel (left) are presented with pins by former U.S. President Bill Clinton during the 20th anniversary National Tribute at the United States Holocaust Memorial Museum April 29, 2013 in Washington, DC. The Museum was hosting a two-day tribute event to honor Holocaust survivors and World War II veterans to mark its 20th anniversary. (Olivier Douliery/Abaca Press/MCT)

The words "Never Again" are projected onto the ceiing of a tent during an event marking the 20th anniversary of the United States Holocaust Memorial Museum in Washington, Monday, April 29, 2013. (AP Photo/Charles Dharapak)